-LRB- CNN -RRB- -- Just four days after winning her fifth Wimbledon crown , Serena Williams overcame the effects of jet lag to successfully begin the defense of her Bank of the West Classic title in Stanford , California .

The American made a smooth transition from the London grass courts -- which she will return to for the Olympics later this month -- and an eight-hour time difference as she beat college champion Nicole Gibbs 6-2 6-1 in the second round of the hard-court event .

`` I definitely felt a little sluggish today , but it was fine , and it was good to get that win , '' Williams told reporters after winning against the 19-year-old wildcard entrant to register her 25th victory in 26 matches .

`` It 's really bright out there too -- I was so used to all the gloom in London and all the clouds

`` I 'll feel better after having tomorrow off and more time to get adjusted . I 'm still waking up at like two in the morning . ''

Gibbs , who is also the NCAA doubles champion , idolized Williams as a child , even serving as a ballgirl for her at age 12 .

`` When I played Monica Seles for the first time it was pretty cool . To think someone would still want to be like me is kind of awesome , '' the 30-year-old Williams said .

Gibbs won her opening match against Thailand 's world No. 174 Noppawan Lertcheewakarn , who did not make it through qualifying at Wimbledon , but found a much tougher challenge in 14-time grand slam champion Williams .

`` It was a great experience -- it was really good to match up against that level and see what 's out there , '' said Gibbs , who was appearing in the main draw of a WTA Tour event for the first time .

`` She 's such a hero in my mind and so built up in my mind , but I think I was definitely more in the match than I had anticipated being . After a few points I felt I could at least compete at that level . ''

Williams was full of praise for her opponent too , adding , `` I think she played really well -- she moves really well and she does n't quit , and I think that 's the best quality you can have as an athlete , and especially as a tennis player .

`` She could have easily given up and she did n't . She 's a fighter . And she has a really good first serve . I think she really held her own today . ''

Williams will next face sixth seed Chanelle Scheepers after the South African beat Portuguese wildcard Michelle Larcher de Brito to reach her first top-level quarterfinal .

`` Serena will definitely be a challenge , but I 'm ready to go out and just enjoy it , '' said Scheepers , who lost to Williams in straight sets in their only previous meeting .

`` I 'm happy with how the hard-court season has started and I hope to keep this up . ''

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Serena Williams wins her first match just four days after victory in the Wimbledon final

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American returned to the U.S. to defend her title at Stanford hard-court event

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Teen opponent idolized Williams as a child , and was even her ballgirl at age 12

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Williams will face South African sixth seed Scheepers in quarterfinals